2. Field of the Invention
The invention relates to the field of metallurgy, and more specifically flux-cored wires, by means of which sulphur is introduced to baths of molten metal, in particular steel and metal alloys.
2. Description of the Related Art
Flux-cored wire with sulphur powder is introduced into molten steel in order to improve the machinability of the final steel by promoting the formation of brittle chips which are removed more rapidly when the components are machined. Sulphur further reduces wear of cutting tools owing to the lubrication effect brought about by non-metallic inclusions which contain it and improves the surface condition of those tools. Addition by means of flux-cored wire allows satisfactory precision to be achieved concerning the quantity of sulphur added, particularly if it must be a relatively small amount in relation to the total mass of molten metal involved.
Such a flux-cored wire is composed of a metal sheath containing a compacted sulphur-based powder. The production of the wire, as for flux-cored wires containing other types of additive, such as calcium silicate, may conventionally begin with powdered sulphur being dispensed by means of gravitational force onto a moving metal strip. The strip must have a composition which is compatible with that of the metal, to which the strip has to be added. It is of steel when sulphur has to be added to a bath of molten steel. The strip is then welded or folded on itself by mechanical profiling by means of a roller type device in order to obtain a flux-cored wire which is subsequently calibrated to the desired diameter.
Other methods for preparing flux-cored wire are known, some of which use techniques involving extrusion and cold-rolling.